Deserializes a JSON data stream and creates an instance of the given type.
If the type implements the [iface@Json.Serializable] interface, it will be asked to deserialize all the JSON members into their respective properties; otherwise, the default implementation will be used to translate the compatible JSON native types.
**Note**: the JSON data stream must be an object
| gtype |
the type of the object to construct |
| data |
a JSON data stream |
| length |
length of the data stream, or -1 if it is `NUL`-terminated |
|
a new object instance of the given type |